President Obama is to tour the beleaguered state of New Jersey on Wednesday, as large swathes of the US east coast attempt to recover from the worst affects of floods, fires and power outages whipped up by superstorm Sandy.

Some of the most densely populated areas of the eastern United States awoke to continued disruption and scenes of devastation, with many areas still inundated with saltwater flooding, downed trees and scattered debris.

The death toll currently stands at 55 and many people faced a miserable night as temperatures fell to freezing. Millions of homes and business were still without power, causing further fears for people's safety.

JFK airport in New York and Newark airport in New Jersey were expected to resume flights on Wednesday morning and bridges into Manhattan have been reopened. However, many transport links in and around New York remain closed.

Authorities have warned that the New York subway system will be closed for at least the next four or five days, as water is pumped out of tunnels and stations are repaired. Of the underwater links into Manhattan, only the Lincoln tunnel was open on Wednesday. Of the ferries, only the Hudson ferry was operational.

The New York stock exchange was reopened by Mayor Bloomberg on Wednesday after two days of closure, despite the lack of power in lower Manhattan.

In a briefing on Wednesday evening, Kevin Burke, CEO of the main New York electricity supplier, ConEdison, said much of lower Manhattan would remain without power for days. He said it would take "three to four days" to restore service at a substation at 14th Street and FDR Drive, which serves power to 220,000 people. The substation failed on Monday night after flooding rose to levels that ConEd had not expected.

On Tuesday, New Jersey governor Chris Christie said that he did not expect the Path transit system, which connects New Jersey with New York, to be operational for at least a week.

The latest forecast from the US national weather service warns of further possible flooding from the Potomac river as Sandy makes it way through Pennsylvania, spreading its effects as far as the Great Lakes.

Speaking on Tuesday, mayor Michael Bloomberg said: "We will get through the days ahead by doing what we always do in tough times by standing together, shoulder to shoulder, ready to help a neighbour, comfort a stranger and get the city we love back on its feet."

Footage released on Wednesday by NYPD also showed the extent of flood damage in residential areas of Staten Island, as rescuers were forced to carry out a dramatic rooftop evacuation of five adults and a child and hoist them to safety in a helicopter.

Obama was planning to visit an area near Atlantic City where Sandy hit on Monday night, with particularly devastating effect.

With the presidential election just six days away, Obama cancelled campaign events for the third day to focus on coordinating the response to the superstorm. His Republican rival, Mitt Romney, planned to resume full-scale campaigning in Florida on Wednesday.